Now if we can just figure out the "magic key" for the DX and DXG (and what software tools to use for debricking them)...

The Freescale i.MX31 architecture should be usable with ATK, too. Also, ATK provides RAM kernels mx31_mmc.bin as well as mx31_sd.bin (I suspect the latter might be the right one, but it's left to someone with such a device to try out and read data). I guess they use the mDDR RAM interface, too.